The blood gas figures for normal gas exchange are:

• PIO2 20
• PaO2 13.3 (12-14)
• PaCO2 5.3 (5-6)
• (PaO2 + PaCO2) 18.6
• PIO2 - (PaO2+PaCO2) 1.4 (less than 2.5)

Check with local laboratory reference values.